This invention relates to electromechanical assemblies; and in particular, it relates to assemblies of the type that include a plurality of printed circuit (P.C.) boards which are mechanically held in place by respective card guides in a frame and are electrically coupled together by conductors on a backplane.
One function of the card guides is to align the boards such that power conductors, ground conductors and signal conductors on the board align with corresponding conductors on the backplane. In operation, boards are inserted into the assembly by sliding them in the card guides toward the backplane until the corresponding conductors engage; and boards are removed from the assembly by sliding them in the card guides in an opposite direction.
However, the boards must fit loosely between the card guides so that they can move freely with little friction. But this, in turn, causes the conductors on the board to be in misalignment with the corresponding conductors on the backplane. Consequently, damage can occur to those conductors when the card is inserted into the assembly.
Also, static charge can accumulate on a board as it is handled prior to insertion into the assembly. Then, when the board is inserted, the static charge is transmitted along the conductors on the backplane to other boards in the assembly where it can destroy various components, such as an integrated circuit chip.
Further, when a component on one of the boards in the assembly becomes defective, it is desirable to be able to replace that board without having to power the assembly down and then power it back up. Typically, one or more memory boards are included in the assembly, and re-initializing data in that memory after powering on can take a long time. But replacing a board in a conventional assembly with power on generates spurious signals on the backplane conductors; and that can cause circuitry on the remaining boards of the assembly to malfunction.
Accordingly, a primary object of the invention is to provide an improved electromechanical assembly of printed circuit boards.
Still another, more specific, object of the invention is to provide an electromechanical assembly which accurately aligns conductors on a printed circuit board with corresponding conductors on a backplane, removes electrostatic charge from the board, and connects the corresponding conductors on the board and backplane in a fashion that enables the board to be inserted and removed with power on.